Biocidal compositions and use thereof containing a synergistic mixture of 2-bromo-2-nitropropane-1,3-diol and n-alkyl dimethyl benzyl ammonium chloride

ABSTRACT

Bactericidal composition and method for inhibiting and controlling the growth of the capsulated, facultative bacterium, Klebsiella pneumoniae, are disclosed. The composition comprises an amount, effective for the intended purpose, of n-alkyl dimethyl benzyl ammonium chloride and 2-bromo-2-nitropropane-1,3-diol. The method comprises administering between about 0.1 to about 200 parts of this combined treatment (based on one million parts of the desired aqueous system) to the particular water containing system for which treatment is desired.

BACKGROUND OF THE INVENTION

The formation of slimes by microorganisms is a problem that isencountered in many aqueous systems. For example, the problem is notonly found in natural waters such as lagoons, lakes, ponds, etc. andconfined waters as in pools, but also in such industrial systems ascooling water systems, air washer systems and pulp and paper millsystems. All possess conditions which are conducive to the growth andreproduction of slime-forming microorganisms. In both once-through andrecirculating cooling systems, for example, which employ largequantities of water as a cooling medium, the formation of slime bymicroorganisms is an extensive and constant problem.

Airborne organisms are readily entrained in the water from coolingtowers and find this warm medium an ideal environment for growth andmultiplication. Aerobic and heliotropic organisms flourish on the towerproper while other organisms colonize and grow in such areas as thetower sump and the piping and passages of the cooling system. The slimeformation not only aids in the deterioration of the tower structure inthe case of wooden towers, but also, by its deposition on metalsurfaces, promotes corrosion. In addition, slime carried through thecooling system plugs and fouls lines, valves, strainers, etc. anddeposits on heat exchange surfaces. In the latter case, the impedance ofheat transfer can greatly reduce the efficiency of the cooling system.

In pulp and paper mill systems, slime formed by microorganisms iscommonly encountered and causes fouling, plugging, or corrosion thereof.The slime also becomes entrained in the paper produced to causebreakouts on the paper machines, with consequent work stoppages and theloss of production time, and/or is responsible for unsightly blemishesin the final product, which results in rejects and wasted output.

The previously discussed problems have resulted in the extensiveutilization of biocides in cooling water and pulp and paper millsystems. Materials which have enjoyed widespread use in suchapplications include chlorine, chlorinated phenols, organo-bromines, andvarious organo-sulfur compounds. All of these compounds are generallyuseful for this purpose but each is attended by a variety ofimpediments. For example, chlorination is limited both by its specifictoxicity for slime-forming organisms at economic levels and by thetendency of chlorine to react, which results in the expenditure of thechlorine before its full biocidal function is achieved. Other biocidesare attended by odor problems and hazards in respect to storage, use orhandling which limit their utility. To date, no one compound or type ofcompound has achieved a clearly established predominance in respect tothe applications discussed. Likewise, lagoons, ponds, lakes, and evenpools, either used for pleasure purposes or used for industrial purposesfor the disposal and storage of industrial wastes, become, during thewarm weather, beseiged by slime due to microorganism growth andreproduction. In the case of the recreational areas the problem ofinfection is obvious. In the case of industrial storage or disposal ofindustrial materials, the microorganisms cause additional problems whichmust be eliminated prior to the material's use or disposal of the waste.

Naturally, economy is a major consideration in respect to all of thesebiocides. Such economic considerations attach to both the cost of thebiocide and the expense of its application. The cost performance indexof any biocide is derived from the basic cost of the material, itseffectiveness per unit of weight, the duration of its biocidal orbiostatic effect in the system treated, and the ease and frequency ofits addition to the system treated. To date, none of the commerciallyavailable biocides has exhibited a prolonged biocidal effect. Instead,their effectiveness is rapidly reduced as the result of exposure tophysical conditions such as temperature, association with ingredientscontained by the system toward which they exhibit an affinity orsubstantivity, etc., with a resultant restriction or elimination oftheir biocidal effectiveness, or by dilution.

As a consequence, the use of such biocides involves their continuous orfrequent addition to systems to be treated and their addition to aplurality of points or zones in the systems to be treated. Accordingly,the cost of the biocide and the labor cost of such means of applying itare considerable. In other instances, the difficulty of access to thezone in which slime formation is experienced precludes the effective useof a biocide. For example, if in a particular system there is no accessto an area at which slime formation occurs the biocide can only beapplied at a point which is upstream in the flow system. However, thephysical or chemical conditions, e.g., chemical reactivity, thermaldegradation, etc. which exist between the point at which the biocide maybe added to the system and the point at which its biodical effect isdesired render the effective use of a biocide impossible.

Similarly, in a system experiencing relatively slow flow, such as apaper mill, if a biocide is added at the beginning of the system, itsbiocidal effect may be completely dissipated before it has reached allof the points at which this effect is desired or required. As aconsequence, the biocide must be added at a plurality of points, andeven then a diminishing biocidal effect will be experineced between onepoint of addition to the system and the next point downstream at whichthe biocides may be added. In addition to the increased cost ofutilizing and maintaining plural feed points, gross ineconomies inrespect to the cost of the biocide are experienced. Specifically, ateach point of addition, an excess of the biocide is added to the systemin order to compensate for that portion of the biocide which will beexpended in reacting with other constituents present in the system orexperience physical changes which impair its biocidal activity.

SUMMARY OF THE INVENTION

The biocidal compositions of the present invention comprise, as activeingredients, (1) an n-alkyl (50% C₁₄, 40% C₁₂, 10% C₁₆) dimethyl benzylammonium chloride (hereinafter "quat") and (2)2-bromo-2-nitropropane-1,3-diol (hereinafter "BNPD").

PRIOR ART

BNPD is sold by The Boots Company, Ltd., Nottingham, England, as anindustrial water treatment antibacterial agent.

Similarly, n-alkyl (C₁₂ -C₁₈) dimethyl benzyl ammonium chloride islisted at 21 CFR 176.300 as being a slimicide that may be safely used inthe manufacture of paper and paperboard products that contact food. Useof the quat compounds in various biocidal compositions is also disclosedin U.S. Pat. No. 3,934,025 (Swered et al.); U.S. Pat. No. 3,827,873(Shema et al.); and U.S. Pat. No. 3,881,008 (Shema et al.).

Other patents which may be noted of possible interest include U.S. Pat.Nos. 3,264,172 (Regutti); 3,142,615 (Wehner); 2,906,595 (Pelcak et al.)and 2,409,883 (Migrdichian).

DETAILED DESCRIPTION

Surprisingly, the present inventors have found that mixtures of n-alkyl(50% C₁₄, 40% C₁₂, 10% C₁₆) dimethyl benzyl ammonium chloride (quat) andBNPD are especially efficacious in controlling the growth of bacterialmicrobes, specifically the Klebsiella pneumoniae species. Thisparticular species is a member of the capsulated, facultative class ofbacteria and is generally present in air, water and soil. These bacteriacontinually contaminate open cooling systems and pulping and papermakingsystems and are among the most common slime formers. This slime may beviewed as being a mass of agglomerated cells stuck together by thecementing action of the gelatinous polysaccharide or proteinaceoussecretions around each cell. The slimy mass entraps other debris,restricts water flow and heat transfer, and may serve as a site forcorrosion.

The fact that the Klebsiella species used in the tests is a facultativespecies is important as, by definition, such bacteria may thrive undereither aerobic or anaerobic conditions. Accordingly, by reason ofdemonstrated efficacy in the growth inhibition of this particularspecies, one can expect similar growth inhibition attributes when otheraerobic or anaerobic bacterial species are encountered.

The n-alkyl (50% C₁₄, 40% C₁₂, 10% C₁₆) dimethyl benzyl ammoniumchloride is commercially available from various sources. For instance,it is sold under the trademark "Maquat 1412" from Mason Chemical Co.,"Onyx 8358" from Onyx Chemical Co., or "Hyamine 3500" by Lonza Inc.

As noted above, BNPD is available from The Boots Company, Ltd., and issold under the trademarks "Myacide AS" or "Bronopol." It is a white freeflowing crystalling solid that is readily soluble in cold water. Theproduct is from about 95-100% pure.

In accordance with the present invention, the combined quat:BNPDtreatment may be added to the desired aqueous system in need of biocidaltreatment, in an amount of from about 0.1 to about 200 parts of thecombined treatment to one million parts (by weight) of the aqueousmedium. Preferably, about 5 to about 50 parts of the combined treatmentper one million parts (by weight) of the aqueous medium is added.

The combined treatment is added, for example, to cooling water systems,paper and pulp mill systems, pools, ponds, lagoons, lakes, etc., tocontrol the formation of bacterial microorganisms, which may becontained by, or which may become entrained in, the system to betreated. It has been found that the quat/BNPD compositions and methodsof utilization of the treatment are efficacious in controlling thefacultative bacterium, Klebsiella pneumoniae, which may populate thesesystems. It is thought that the combined treatment composition andmethod of the present invention will also be efficacious in inhibitingand controlling all types of aerobic and anaerobic bacteria.

Surprisingly, it has been found that when the quat/BNPD ingredients aremixed, in certain instances, the resulting mixtures possess a higherdegree of bactericidal activity than that of the individual ingredientscomprising the mixture. Accordingly, it is possible to produce a highlyefficacious bactericide. Because of the enhanced activity of themixture, the total quantity of the bacterial treatment may be reduced.In addition, the high degree of bactericidal effectiveness which isprovided by each of the ingredients may be exploited without use ofhigher concentrations of each.

The following experimental data were developed. It is to be rememberedthat the following examples are to be regarded solely as beingillustrative, and not as restricting the scope of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Quat and BNPD were added in in varying ratios and over a wide range ofconcentrations to a liquid nutrient medium which was subsequentlyinoculated with a standard volume of a suspension of the facultativebacterium Klebsiella pneumoniae. Growth was measured by determining theamount of radioactivity accumulated by the cells when ¹⁴ C-glucose wasadded as the sole source of carbon in the nutrient medium. The effect ofthe biocide chemicals, alone and in combination, is to reduce the rateand amount of ¹⁴ C incorporation into the cells during incubation, ascompared to controls not treated with the chemicals. Additions of thebiocides, alone and in varying combinations and concentrations, weremade according to the accepted "checkerboard" technique described by M.T. Kelley and J. M. Matsen, Antimicrobial Agents and Chemotherapy. 9:440, (1976). Following a two hour incubation, the amount ofradioactivity incorporated in the cells was determined by counting (¹⁴ Cliquid scintillation procedures) for all treated and untreated samples.The percent reduction of each treated sample was calculated from therelationship: ##EQU1##

Plotting the % reduction of ¹⁴ C level against the concentration of eachbiocide acting alone results in a dose-response curve, from which thebiocide dose necessary to achieve any given % reduction can beinterpolated.

Synergism was determined by the method of calculation described by F. C.Kull, P. C. Eisman, H. D. Sylwestrowicz and R. L. Mayer, AppliedMicrobiology 9, 538, (1961) using the relationship: ##EQU2## where:Q_(a) =quantity of compound A, acting alone, producing an end point

Q_(b) =quantity of compound B, acting aline, producing an end point

Q_(A) =quantity of compound A in mixture, producing an end point

Q_(B) =quantity of compound B in mixture, producing an end point

The end point used in the calculations is the % reduction caused by eachmixture of A and B. Q_(A) and Q_(B) are the individual concentrations inthe A/B mixture causing a given % reduction. Q_(a) and Q_(b) aredetermined by interpolation from the respective dose-response curves ofA and B as those concentrations of A and B acting alone which producethe same % reduction as each specific mixture produced.

Dose-response curves for each active acting alone were determined bylinear regression analysis of the dose-response data. Data were fittedto a curve represented by the equation shown with each data set. Afterlinearizing the data, the contributions of each biocide component in thebiocide mixtures to the inhibition of radioisotype uptake weredetermined by interpolation with the dose response curve of therespective biocide. If, for example, quantities of Q_(A) plus Q_(B) aresufficient to give a 50% reduction in ¹⁴ C content, Q_(a) and Q_(b) arethose quantities of A or B acting alone, respectively, found to give 50%reduction in ¹⁴ C content. A synergism index (SI) is calculated for eachcombination of A and B.

Where the SI is <1, synergism exists. Where the SI=1, additivity exists.Where SI>1, antagonism exists.

The data in the following tables come from treating Klebsiellapneumoniae, a common nuisance bacterial type found in industrial coolingwaters and in pulping and paper making systems, with varying ratios andconcentrations of quat and BNPD. Shown for each combination is the %reduction of ¹⁴ C content, the calculated SI, and the weight ratio ofquat to BNPD.

                  TABLE I                                                         ______________________________________                                        BNPD vs. Quat                                                                 ppm      ppm     ratio                                                        BNPD     Quat**  BNPD:Quat     % I  SI                                        ______________________________________                                        0        80       0:100        99                                             0        40       0:100        99                                             0        20       0:100        98                                             0        10       0:100        80                                             0        5        0:100        18                                             0        2.5      0:100         0                                             80       0       100:0         95                                             40       0       100:0         79                                             20       0       100:0         30                                             10       0       100:0          0                                             5        0       100:0          0                                             2.5      0       100:0          0                                             80       80      1:1           99                                             80       40      2:1           99                                             80       20      4:1           99                                             80       10      8:1           98   1.35                                      80       5       16:1          96   1.25                                      80       2.5     32:1          93   1.23                                      40       80      2:1           99                                             40       40      1:1           99                                             40       20      2:1           99                                             40       10      4:1           97   0.81*                                     40       5       8:1           92   0.73*                                     40       2.5     16:1          83   0.75*                                     20       80      1:4           99                                             20       40      1:2           99                                             20       20      1:1           98   0.77*                                     20       10      2:1           96   0.55*                                     20       5       4:1           76   0.60*                                     20       2.5     8:1           26   1.63                                      10       80      1:8           99                                             10       40      1:4           98   1.14                                      10       20      1:2           98   0.64*                                     10       10      1:1           94   0.43*                                     10       5       2:1           42   1.03                                      10       2.5     4:1            0                                             5        80       1:16         99                                             5        40      1:8           98   1.10                                      5        20      1:4           98   0.57*                                     5        10      1:2           94   0.36*                                     5        5       1:1           31   1.21                                      5        2.5     2:1            0                                             2.5      80       1:32         99                                             2.5      40       1:16         98   1.03                                      2.5      20      1:8           97   0.55*                                     2.5      10      1:4           93   0.33*                                     2.5      5       1:2           15   1.88                                      2.5      2.5     1:1            0                                             ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        BNPD vs. Quat                                                                 ppm      ppm     ratio                                                        BNPD     Quat**  BNPD:Quat     % I  SI                                        ______________________________________                                        0        80       0:100        99                                             0        40       0:100        99                                             0        20       0:100        97                                             0        10       0:100        92                                             0        5        0:100        50                                             0        2.5      0:100         0                                             80       0       100:0         93                                             40       0       100:0         75                                             20       0       100:0         27                                             10       0       100:0          0                                             5        0       100:0          0                                             2.5      0       100:0          0                                             80       80      1:1           99                                             80       40      2:1           99                                             80       20      4:1           99                                             80       10      8:1           98   1.34                                      80       5       16:1          97   1.21                                      80       2.5     32:1          92   1.21                                      40       80      1:2           99                                             40       40      1:1           99                                             40       20      2:1           98   1.09                                      40       10      4:1           97   0.82*                                     40       5       8:1           90   0.76*                                     40       2.5     16:1          82   0.76*                                     20       80      1:4           99                                             20       40      1:2           99                                             20       20      1:1           99   0.79*                                     20       10      2:1           95   0.59*                                     20       5       4:1           81   0.58*                                     20       2.5     8:1           15   2.79                                      10       80      1:8           99                                             10       40      1:4           99                                             10       20      1:2           98   0.69*                                     10       10      1:1           94   0.46*                                     10       5       2:1           67   0.65*                                     10       2.5     4:1            0                                             5        80       1:16         99                                             5        40      1:8           99                                             5        20      1:4           98   0.62*                                     5        10      1:2           93   0.40*                                     5        5       1:1           50   0.96                                      5        2.5     2:1            0                                             2.5      80       1:32         99                                             2.5      40       1:16         98   1.14                                      2.5      20      1:8           97   0.60*                                     2.5      10      1:4           93   0.37*                                     2.5      5       1:2           54   0.77*                                     2.5      2.5     1:1            0                                             ______________________________________                                         Asterisks in the SI column indicate synergistic combinations in accordanc     with the Kull method supra. The double asterisk adjacent the Quat compoun     indicates that Quat product containing 80% actives was used.             

In accordance with Tables I-II supra., unexpected results occured morefrequently within the product ratios of BNPD product: Quat product offrom about 16:1 to 1:8. Since the tested Quat product was about 80%active, this range translates to a range of BNPD: Quat (100% activesbasis) of from about 20:1 to about 1:6.4. At present, it is preferredthat the commercial product embodying the invention comprise a weightratio of about 1:3.2 BNPD: Quat.

While we have shown and described herein certain embodiments of thepresent invention, it is intended that there be covered as well anychange or modification therein which may be made without departing fromthe spirit and scope of the invention.

We claim:
 1. A bacterial inhibiting composition comprising a synergisticaqueous mixture of 2-bromo-2-nitropropane-1,3-diol (BNPD) and n-alkyldimethyl benzyl ammonium chloride (quat), wherein said quat comprises analkyl distribution of about (50% C₁₄, 40% C₁₂, 10% C₁₆), wherein theweight ratio of said BNPD to said quat is from about 16:1 to about 1:8.2. A method for controlling the growth of Klebsiella pneumoniae bacteriain an aqueous system which comprises adding to said system from about0.1 to about 200 parts per weight of a synergistic composition per onemillion parts per weight of said aqueous system, said compositioncomprising a mixture of 2-bromo-2-nitropropane-1,3-diol (BNPD) andn-alkyl dimethyl benzyl ammonium chloride (quat), wherein said quatcomprises an alkyl distribution of about (50% C₁₄, 40% C₁₂, 10% C₁₀ ,the weight ratio of said BNPD to quat being from about 16:1 to about1:8.
 3. The method is defined in claim 2 wherein said composition isadded to said system in an amount of from about 5 to about 50 parts permillion of said aqueous system.
 4. The method as defined in claim 2wherein said aqueous system comprises a cooling water system.
 5. Themethod as defined in claim 2 wherein said aqueous system comprises apulping and papermaking system.